1. Field of the Invention
The present invention relates to a substantially solventless, environmentally unburdensome process for preparing a high-grade epoxidized polyalkenylene.
2. Discussion of the Background
Known processes suffer from the use of organic solvents, often aromatic and/or halogenated during the epoxidation and/or workup. These solvents are then difficult to remove from the polymer. Moreover, a variety of epoxidation by-products are poorly soluble in these solvents and may remain in the polymer. Known processes minimize this by adding an extraction step with water or solvent/water mixtures, very often in multistage form. The subsequent separation of the organic phase from the aqueous phase is an additional process step.
Epoxidized polyalkenylenes enjoy a diverse breadth of applications, particularly as agents for surface enhancement and surface sealing, hydrophobization, and for solidifying compounded formulations.
Polyalkenylenes belong to the olefinic polymers group, and thus the addition of an epoxide oxygen onto the double bond in accordance with the Prileshaev reaction is long-established state of the art. The carboxylic acids used for this purpose, such as formic acid, acetic acid (DE-A 25 54 093, U.S. Pat. No. 4,309,516), benzoic or propionic acid (DE-A 32 38 886), remain in part in the epoxidized polymers after the product has been isolated, or must be removed by means of purification techniques, which are very complex. Additionally, the organic solvent must be separated from the water. DE-A 35 28 007 describes a process in which the epoxidation step in benzene, performed by means of perpropionic acid, is followed by thirteen washing and distillation stages for removing the carboxylic acid and the solvent. Given the ready solubility of benzene in the polyalkenylene, moreover, it can be assumed that a fraction of benzene will remain in the product. Other processes (FR 2 320 972, DE A 25 42 709) use monoperphthalic acid, which is subsequently separated by time-consuming and solvent-consuming filtration. However, it can be assumed that despite the great effort it will be impossible to completely separate off the acid, due to a certain solubility in the epoxidized polymer.
Other transition-metal-catalyzed epoxidations suffer from the difficulty of preparing the catalysts and their costliness (J. Polym. Sci., Part C: Poly Lett. 1990, 28, 285; Polym. Chem. 1991, 29, 547) and/or the burdensome technological conditions which their use dictates (phase transfer catalysis: WO 9 828 338). Again, this is followed by the separation of the organic solvents.
DE-A 32 38 886 describes the epoxidation of conjugated diolefin polymers and vegetable oils in solvents (examples), although this is not the subject matter of the invention. Even if the epoxidation step in water were successful, the subsequent extraction would be impossible without an additional solvent (isopropanol).
It is therefore an object of the present invention to provide a substantially solventless epoxidation process which avoids the use of environmentally harmful solvents at all stages, thereby minimizing the washing effort, and which provides a high-grade product.
Another object of the present invention is to provide effective catalysts for use in epoxidation processes.
These and other objects have been achieved by the present invention the first embodiment of which includes a process for preparing an epoxidized polyalkenylene, comprising:
reacting a polyalkenylene, an aqueous solution of 15 to 90% by volume of hydrogen peroxide and a carboxylic acid having from 1 to 3 carbon atoms in the presence of a catalyst comprising a member selected from the group consisting of phosphonic acid, a derivative of phosphonic acid, and mixtures thereof, without addition of an organic solvent or water, to obtain said epoxidized polyalkenylene;
wherein said epoxidized polyalkenylene has a number-average molar mass of between 500 and 50 000 g/mol; and
wherein said epoxidized polyalkenylene has an epoxide oxygen content of between 1 and 25% by mass.
The present invention provides a process for preparing an epoxidized polyalkenylene having a number-average molar mass of between 500 and 50 000 g/mol and an epoxide oxygen content of between 1 and 25 percent by mass by reacting a polyalkylene, from 15 to 90% strength hydrogen peroxide, and a carboxylic acid having from 1 to 3 carbon atoms in the presence of a phosphonic acid and/or derivatives thereof as catalyst, without further addition of organic solvents or water. 15 to 90% strength hydrogen peroxide in the context of the present invention means an aqueous solution having 15 to 90% by volume of hydrogen peroxide. The number-average molar mass of the epoxidized polyalkenylene includes all values and subvalues therebetween, especially including 1000, 5000, 10000, 15000, 20000, 25000, 30000, 35000, 40000 and 45000 g/mol. The epoxide oxygen content of the epoxidized polyalkenylene includes all values and subvalues therebetween, especially including 5, 10, 15 and 20%. The strength of the hydrogen peroxide includes all values and subvalues therebetween, especially including 20, 30, 40, 50, 60, 70 and 80%.
The epoxidation reaction is conducted at a temperature of from 10 to 100xc2x0 C., preferably 20 to 60xc2x0 C. The reaction temperature includes all values and subvalues therebetween, especially including 20, 30, 40, 50, 60 70, 80 and 90xc2x0 C.
The process of the invention resolves the above disadvantages of existing processes because the epoxidation takes place without the use of a solvent. An advantageous feature is that, in the subsequent workup of the products, water alone can be used as extractant. It has been found that there is no residue of free carboxylic acids in the epoxidized product when short-chain carboxylic acids (C1-C3) are used. Free carboxylic acids might be a cause of uncontrolled crosslinking of the epoxidized polyalkylene. The substances used as catalyst for the process are, surprisingly, highly active and effective, dissolving poorly in the polymer but very readily in water. Accordingly, they are very simple to separate from the reaction mixture. The process is preferably conducted in the presence of at least one aminophosphonic acid catalyst.
It has likewise been found, surprisingly, that the phosphonic acids and their derivatives, especially the aminophosphonic acids, are suitable catalysts in the preparation of epoxidation products from polyalkenylenes.
The present invention accordingly further provides for the use of phosphonic acid and/or derivatives thereof as catalysts in the preparation of epoxidation products from polyalkenylenes. Particularly preferred aminophosphonic acids are those specified in greater detail later on below. In principle, the catalysts may be used in both solventless and solvent-mediated processes. In addition, the organic peracid may be used directly or generated in situ. Preference is given to C1-C3 carboxylic acids, such as formic, acetic and/or propionic acid.
With particular preference, the catalysts are used in processes which are conducted substantially or totally without solvent.
Suitable polyalkenylene starting materials are preferably polymers based on monomeric dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and chloroprene. It is possible to use homopolymers or else copolymers of the aforementioned monomers, but preferably homopolymers, especially those of 1,3-butadiene. The polyalkenylenes may be 1,4- or 1,2-linked. Also possible, however, are mixtures of 1,2- and 1,4-linkages, in which case the 1,4-linkage can adopt both cis and trans arrangements. Very particular preference is given to a polybutadiene containing about 75% 1,4-cis, about 24% 1,4-trans, and about 1% 1,2-double bonds (Polyoil, Degussa).
Furthermore, it is also possible to use polyalkenylenes constructed from at least one of the abovementioned monomeric dienes and one or more vinyl compounds and/or alkenes. Examples of preferred vinyl compounds include styrenes and substituted styrenes, vinyl ethers, and acrylates or methacrylates. Examples of preferred alkenes include ethene, propene, butene, and isobutene.
Preferred carboxylic acids are formic, acetic or propionic acid, alone or in mixtures.
Phosphonic acid and/or derivatives thereof are used as catalysts. Particularly preferred catalysts are aminophosphonic acids, such as aminotrismethylenephosphonic acid (ATMP) (6419-19-8), aminotris(1-methyl-2,1-ethanediyl)phosphonic acid (107559-74-0), {aminotris(1-methylethylidene)}trisphosphonic acid (29557-57-1), {{(phosphonomethyl)imino}di-2,1-ethanediyl}bisphosphonic acid (220659-04-1), aminotrisetbylidenephosphonic acid (24573-69-1), [1-{bis(phosphonomethyl)amino}ethyl}phosphonic acid (45203 32 5), aminotrispropylidenephosphonic acid (45265-40-5), {{(2-phosphonoethyl)imino}bis(methylene)}bisphosphonic acid (68593-88-4), {1,2-ethanediylbis{aminobis(methylene)}}tetrakisphosphonic acid (1429-50-1), {1,3-propanediylbis{aminobis(methylene)}}tetrakisphosphonic acid (28444-52-2), N2,N2,N5,N5-tetrakis(phosphonomethyl)omithine (193553 86 5), {methylenebis{aminobis(methylene)}}tetrakisphosphonic acid (70235-52-8) (CA Registry numbers). Mixtures are also suitable. The amount of catalysts used may vary from 0.05 to 500 mmol per mole of polyalkenylene. The amount of catalyst includes all values and subvalues therebetween, especially including 1, 5, 10, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400 and 450 mmol.
The present invention further provides for the use of the epoxidized polyalkenylenes prepared in accordance with the present invention as reactants for polymer-analogous reactions and as ingredients in crosslinking systems. In accordance with the present invention they are used for preparing binders, adhesives, sealants, coating materials, and plasticizers, especially for producing paints, printing inks, printing plates, and soundproofing compositions.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only, and are not intended to be limiting unless otherwise specified.